1. Field of Invention
The present invention generally relates to a method, article of manufacture, and apparatus for processing wafers in a semiconductor wafer processing system. More particularly, the present invention provides a processing sequence in which wafers are at least partially preheated in transition chambers in a semiconductor wafer processing system.
2. Description of the Related Art
Semiconductor wafer processing systems comprising an integrated unit which contains multiple processing chambers are well known in the art. The integrated unit reduces contamination in the system components and increases the throughput of the system. An example of a semiconductor wafer processing sytem with such a unit is the Endura® platform available from Applied Materials, Inc. of Santa Clara, Calif. The Endura® platform has a pre-metallization cluster with chambers in which wafers are entered, oriented, degassed, sputter cleaned, and cooled and at least one metallization cluster of processing chambers wherein metal deposition is performed. The pre-metallization and metallization clusters are connected by transition or pass-through chambers.
Typically, the only components of an integrated unit of a semiconductor wafer processing system that are vented to the atmosphere during processing are wafer load locks through which wafers enter and exit from the system. Single or batch wafer load locks can be used. Single wafer load locks are small and deliver one or two wafers to the system, while batch wafer load locks are larger and deliver more wafers. Single wafer load locks are often preferred because their smaller volumes do not require as much time to transition to the desired vacuum pressure from atmospheric pressure as batch wafer load locks.
Wafer load locks which can perform required pre-processing and post-processing steps on wafers have been developed. For example, a single wafer load lock can include a heating element to preheat a wafer before further processing. Preheating may also be used to degas a wafer, i.e., remove contaminants from the wafer surface. Other pre-processing cleaning may also be performed in the load lock. A single wafer load lock can also function as a cool-down chamber to cool a wafer that has been treated in a processing chamber. Including pre- and post-processing functions in single wafer load locks eliminates the need for separate pre- and post-processing chambers and reduces the time required to transfer a wafer into and out of such chambers.
An important aspect in the processing of wafers in a semiconductor wafer processing system is the number of wafers that pass through the system in a certain amount of time, which is called the throughput of the system. While wafer load locks with pre- and post-processing functions have improved the throughput of semiconductor wafer processing systems such as the Endura® platform, greater increases in throughput are desired. In some cases, the slowest step in the integrated unit of a semiconductor wafer processing system is the pre-processing step in the single wafer load lock. Thus, a method and apparatus for faster pre-processing is needed.